The present invention relates to integrated circuits.
In some embodiments of the present invention, one or more openings are formed in an active side of a semiconductor wafer, a dielectric is formed in the openings, and a conductor (e.g. metal) is formed in the openings over the dielectric. Then the wafer is etched from the backside to expose the conductor. The openings become through holes, and the exposed conductor provides contacts protruding from the through holes. Each contact has a protruding outer surface not covered by the dielectric. At least a portion of the outer surface is either vertical or is sloped outwards (laterally away from the corresponding through hole) when the surface is traced in the direction away from the wafer. The protruding contacts are soldered to some substrate (e.g. another wafer or a printed circuit board). The solder reaches and at least partially covers the contacts"" surface that is vertical or sloped outwards. Consequently, the strength of the solder bond is increased.
In some embodiments, the dielectric forms a protrusion around each contact. Throughout the protrusion, the dielectric becomes gradually thinner around each contact as the dielectric is traced in the direction away from the wafer. The thinner dielectric is more flexible, and therefore is less likely to detach from the contact if the contact is pulled sideways.
Other embodiments and variations are within the scope of the invention. The invention is defined by the appended claims.